Passenger vehicles, particularly commercial aircraft, have seat installations which include jacks i.e. sockets for receiving connector plugs for headsets or headphones. Thus a user can provide his or her own headset, or be provided with a headset by an attendant on the vehicle and can plug the headset into the jack provided on the relevant seat to listen to various audio channels.
Typically, the audio information is provided in the form of an electric signal that is passed by electric connections between the jack and the plug to the headset.
Recent developments to passenger audio systems include noise reduction headphones. There have been many attempts to create noise reduction headphones for use onboard commercial passenger aircraft. There are presently several embodiments of noise reduction systems, and most have their own particular headset plug and jack arrangement.
For example, in one noise reduction system there is an electronic circuit providing noise reduction functionality located in a medallion at arms length and separate to the headphone. The headphone must interface to the noise reduction circuit via a connector and jack of some description. One such connector comprises a standard 3.5 mm stereo plug in combination with a 2.5 mm stereo plug providing six potential signal lines.
In another example, the electronic circuit providing noise reduction functionality is located within or adjacent to the headphone i.e. as an adjunct to the headphones. This circuit may require power and therefore a connector providing stereo audio and power is necessary. One such connector uses a three prong configuration (i.e. three pins from the plug) comprising two 3.5 mm mono plugs in combination with a single 2.5 mm mono plug. This provides the capacity for six independent signal lines, of which four independent signal lines are typically used.
In all cases the use of the three prong jack to enable connection of a headphone with adjunct circuit removes the possibility of easily deploying an alternative system such as that where the noise reduction circuit is located at arms length to the headphone and vice versa. This is because the different plug and jack arrangements mean that to switch from one system to another means changing the jack and associated cabling. Therefore, variations in jack configuration create an unnecessary barrier for the operator to frequently change or upgrade the way in which active noise reduction and audio in general is delivered to passengers via headphones. The other disadvantage with the variations in jack configuration is that it makes it cumbersome to interconnect variations of similar technology, which require, in most cases, the same signal lines to operate.